combine two AoHs

alienhuman has asked for the wisdom of the Perl Monks concerning the following question:

Monks,

I've got two AoHs, and each hash shares a key, like so:

#!/usr/bin/perl

use strict;
use Data::Dumper;

my @a = ({ domain => 'adomain.com',
          data => 'adata',
        },
        { domain => 'bdomain.com',
          data => 'bdata',
        });

my @b = ({ domain => 'adomain.com',
          otherdata => 'astuff',
        },
        { domain => 'bdomain.com',
          otherdata => 'bstuff',
        });
[download]

I want to end up with a single AoH that looks like this:

@c = ({ domain => 'adomain.com',
       otherdata => 'astuff',
       data => 'adata',
     },
     { domain => 'bdomain.com',
       otherdata => 'bstuff',
       data => 'bdata',
     });
[download]

Just can't get my head around how to do this...

----------

Using perl 5.8.1-RC3 unless otherwise noted.
Apache/1.3.33 (Darwin) unless otherwise noted.
Mac OS X 10.3.9 unless otherwise noted.
[download]

Comment on combine two AoHs Select or Download Code

Replies are listed 'Best First'.
Re: combine two AoHs by diotalevi (Canon) on Mar 06, 2006 at 22:37 UTC
This merges the list of hashes by storing them temporarilly in the %merge hash and indexing them by 'domain'. You can omit the $to_merge temporary if you're willing to get a bit more ugly syntax. `my @c = merge_aoh_by_domain( @a, @b ); sub merge_aoh_by_domain { my %merge; for my $domain_ref ( @_ ) { # less ugly my $to_merge = $merge{$domain_ref->{domain}} \|\|= {}; @$to_merge{ keys %$domain_ref } = values %$domain_ref; # ugly # @{$merge{$domain_ref->{domain}}{ keys %$domain_ref } = value +s %$domain_ref; } return values %merge; }` [download] ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊	[reply] [d/l]
Re: combine two AoHs by ambrus (Abbot) on Mar 06, 2006 at 22:28 UTC
`@c = map { +{%{$a[$_]}, %{$b[$_]}} } 0 .. @a - 1;` [download] Update: it appears that I've interpreted your question differently from diotalevi. Here's an example on when they're different. Read more... (2 kB)	[reply] [d/l] [select]
Re^2: combine two AoHs by alienhuman (Pilgrim) on Mar 07, 2006 at 01:18 UTC
Thanks to all three of you, but in particular ambrus, for demonstrating how the two methods differ. diotalevi gets bonus points for interpreting my poorly articulated question correctly ;-) AH ---------- `Using perl 5.8.1-RC3 unless otherwise noted. Apache/1.3.33 (Darwin) unless otherwise noted. Mac OS X 10.3.9 unless otherwise noted.` [download]	[reply] [d/l]
Re: combine two AoHs by GrandFather (Saint) on Mar 06, 2006 at 22:51 UTC
map and a little casting magic does the trick. Note the `%{$a[$_]}` that turns the hash ref returned by `$a[$_]` into a hash. BTW, you should perhaps avoid using a and b - even when they are not scalars they can cause confusion due to $a and $b being used for sort parameters. (Yes, I know this is a trivial sample, but good habits are good habits.) `use strict; use warnings; use Data::Dump::Streamer; my @a_ = ({ domain => 'adomain.com', data => 'adata', }, { domain => 'bdomain.com', data => 'bdata', }); my @b_ = ({ domain => 'adomain.com', otherdata => 'astuff', }, { domain => 'bdomain.com', otherdata => 'bstuff', }); my @c = map {{%{$a_[$_]}, %{$b_[$_]}}} 0..$#a_; Dump (\@c);` [download] Prints: `$ARRAY1 = [ { data => 'adata', domain => 'adomain.com', otherdata => 'astuff' }, { data => 'bdata', domain => 'bdomain.com', otherdata => 'bstuff' } ];` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]